brcmfmac: Use fw filename and nvram based of devid for sdio.

SDIO firmware download routines uses one name for firmware file
and nvram file for all sdio devices. This is not user friendly.
Use fw filename and nvram filename based upon chip id and revision.

Reported-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>